Methods and systems for devices with self-selecting bus decoder

ABSTRACT

Disclosed are methods and devices, among which is a device including a self-selecting bus decoder. In some embodiments, the device may be coupled to a microcontroller, and the self-selecting bus decoder may determine a response of the peripheral device to requests from the microcontroller. In another embodiment, the device may include a bus translator and a self-selecting bus decoder. The bus translator may be configured to translate between signals from a selected one of a plurality of different types of buses. A microcontroller may be coupled to a selected one of the plurality of different types of buses of the bus translator.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/268,270, entitled “Methods and Systems for Devices withSelf-selecting Bus Decoder”, filed Nov. 10, 2008, which is hereinincorporated by reference, now U.S. Pat. No. 8,402,188, which issued onMar. 19, 2013.

BACKGROUND

Field of Invention

Embodiments of the invention relate generally to electronic devices and,more specifically, in certain embodiments, to electronic devices havinga bus translator.

Description of Related Art

In the field of computing, pattern recognition tasks are increasinglychallenging. Ever larger volumes of data are transmitted betweencomputers, and the number of patterns that users wish to identify isincreasing. For example, spam or malware are often detected by searchingfor patterns in a data stream, e.g., particular phrases or pieces ofcode. The number of patterns increases with the variety of spam andmalware, as new patterns may be implemented to search for new variants.Searching a data stream for each of these patterns can form a computingbottleneck. Often, as the data stream is received, it is searched foreach pattern, one at a time. The delay before the system is ready tosearch the next portion of the data stream increases with the number ofpatterns. Thus, pattern recognition may slow the receipt of data.

Hardware that performs pattern recognition has been designed, and thishardware is believed to be capable of searching a data stream for arelatively large number of patterns relatively quickly. However,implementing this hardware is complicated by the variety of devices withwhich the hardware might interface. Pattern-recognition devices, andassociated peripheral devices, may be coupled to a variety of differenttypes of devices, e.g., microcontrollers. “Single-chip microcontrollers”are microprocessors that typically have integrated functions such asprogram storage, data storage, interfaces etc. Such microcontrollers areoften designed for a dedicated and specific functionality and/or device.

However, because microcontrollers often provide these integratedfunctions at a lower cost, adding additional program storage, datastorage, or other functions may increase the cost of themicrocontroller, reducing the feasibility of use of the microcontrollerin a system or device. For example, the addition of memory, such as RAM,ROM, etc, often includes the addition of a memory management unit.Further, such microcontrollers often have multiplexed buses to reducedie size, package size, etc. Typically, an added function will alsoinclude a gate-array device to perform bus translation. Themicrocontroller may not have the power and/or the space to implementthese additional components, and such external functions may not becost-feasible.

Further, additional features or enhancement to such microcontrollers mayemploy more program or data storage in the form or RAM, ROM, or othermemory. Because of the challenges described above, system developersoften must wait for newer microcontroller having the desired features,or more expensive microcontrollers with the features added externally.Further, as described above, adding additional or enhanced functionsoften creates die size, power, and cost challenges.

This issue is not limited to pattern-recognition devices. Other devicesthat communicate with microcontrollers face similar issues. Any added orenhanced functionality to a microcontroller may encounter the challengesdescribed above.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 depicts an example of system that searches a data stream;

FIG. 2 depicts an example of a pattern-recognition processor in thesystem of FIG. 1;

FIG. 3 depicts an example of a search-term cell in thepattern-recognition processor of FIG. 2;

FIGS. 4 and 5 depict the search-term cell of FIG. 3 searching the datastream for a single character;

FIGS. 6-8 depict a recognition module including several search-termcells searching the data stream for a word;

FIG. 9 depicts the recognition module configured to search the datastream for two words in parallel;

FIGS. 10-12 depict the recognition module searching according to asearch criterion that specifies multiple words with the same prefix;

FIG. 13 depicts an embodiment of a peripheral device having aself-selecting bus decoder coupled to a microcontroller;

FIG. 14 depicts further details the embodiment the peripheral device andbus decoder depicted in FIG. 13;

FIG. 15 depicts another embodiment of a peripheral device having aself-selecting bus decoder and a bus translator; and

FIG. 16 depicts an embodiment of a process of operation of theperipheral device having a self-selecting bus decoder.

DETAILED DESCRIPTION

FIG. 1 depicts an example of a system 10 that searches a data stream 12.The system 10 may include a pattern-recognition processor 14 thatsearches the data stream 12 according to search criteria 16.

Each search criterion may specify one or more target expressions, i.e.,patterns. The phrase “target expression” refers to a sequence of datafor which the pattern-recognition processor 14 is searching. Examples oftarget expressions include a sequence of characters that spell a certainword, a sequence of genetic base pairs that specify a gene, a sequenceof bits in a picture or video file that form a portion of an image, asequence of bits in an executable file that form a part of a program, ora sequence of bits in an audio file that form a part of a song or aspoken phrase.

A search criterion may specify more than one target expression. Forexample, a search criterion may specify all five-letter words beginningwith the sequence of letters “cl”, any word beginning with the sequenceof letters “cl”, a paragraph that includes the word “cloud” more thanthree times, etc. The number of possible sets of target expressions isarbitrarily large, e.g., there may be as many target expressions asthere are permutations of data that the data stream could present. Thesearch criteria may be expressed in a variety of formats, including asregular expressions, a programming language that concisely specifiessets of target expressions without necessarily listing each targetexpression.

Each search criterion may be constructed from one or more search terms.Thus, each target expression of a search criterion may include one ormore search terms and some target expressions may use common searchterms. As used herein, the phrase “search term” refers to a sequence ofdata that is searched for, during a single search cycle. The sequence ofdata may include multiple bits of data in a binary format or otherformats, e.g., base ten, ASCII, etc. The sequence may encode the datawith a single digit or multiple digits, e.g., several binary digits. Forexample, the pattern-recognition processor 14 may search a text datastream 12 one character at a time, and the search terms may specify aset of single characters, e.g., the letter “a”, either the letters “a”or “e”, or a wildcard search term that specifies a set of all singlecharacters.

Search terms may be smaller or larger than the number of bits thatspecify a character (or other grapheme—i.e., fundamental unit—of theinformation expressed by the data stream, e.g., a musical note, agenetic base pair, a base-10 digit, or a sub-pixel). For instance, asearch term may be 8 bits and a single character may be 16 bits, inwhich case two consecutive search terms may specify a single character.

The search criteria 16 may be formatted for the pattern-recognitionprocessor 14 by a compiler 18. Formatting may include deconstructingsearch terms from the search criteria. For example, if the graphemesexpressed by the data stream 12 are larger than the search terms, thecompiler may deconstruct the search criterion into multiple search termsto search for a single grapheme. Similarly, if the graphemes expressedby the data stream 12 are smaller than the search terms, the compiler 18may provide a single search term, with unused bits, for each separategrapheme. The compiler 18 may also format the search criteria 16 tosupport various regular expressions operators that are not nativelysupported by the pattern-recognition processor 14.

The pattern-recognition processor 14 may search the data stream 12 byevaluating each new term from the data stream 12. The word “term” hererefers to the amount of data that could match a search term. During asearch cycle, the pattern-recognition processor 14 may determine whetherthe currently presented term matches the current search term in thesearch criterion. If the term matches the search term, the evaluation is“advanced”, i.e., the next term is compared to the next search term inthe search criterion. If the term does not match, the next term iscompared to the first term in the search criterion, thereby resettingthe search.

Each search criterion may be compiled into a different finite statemachine in the pattern-recognition processor 14. The finite statemachines may run in parallel, searching the data stream 12 according tothe search criteria 16. The finite state machines may step through eachsuccessive search term in a search criterion as the preceding searchterm is matched by the data stream 12, or if the search term isunmatched, the finite state machines may begin searching for the firstsearch term of the search criterion.

The pattern-recognition processor 14 may evaluate each new termaccording to several search criteria, and their respective search terms,at about the same time, e.g., during a single device cycle. The parallelfinite state machines may each receive the term from the data stream 12at about the same time, and each of the parallel finite state machinesmay determine whether the term advances the parallel finite statemachine to the next search term in its search criterion. The parallelfinite state machines may evaluate terms according to a relatively largenumber of search criteria, e.g., more than 100, more than 1000, or morethan 10,000. Because they operate in parallel, they may apply the searchcriteria to a data stream 12 having a relatively high bandwidth, e.g., adata stream 12 of greater than or generally equal to 64 MB per second or128 MB per second, without slowing the data stream. In some embodiments,the search-cycle duration does not scale with the number of searchcriteria, so the number of search criteria may have little to no effecton the performance of the pattern-recognition processor 14.

When a search criterion is satisfied (i.e., after advancing to the lastsearch term and matching it), the pattern-recognition processor 14 mayreport the satisfaction of the criterion to a processing unit, such as acentral processing unit (CPU) 20. The central processing unit 20 maycontrol the pattern-recognition processor 14 and other portions of thesystem 10.

The system 10 may be any of a variety of systems or devices that searcha stream of data. For example, the system 10 may be a desktop, laptop,handheld or other type of computer that monitors the data stream 12. Thesystem 10 may also be a network node, such as a router, a server, or aclient (e.g., one of the previously-described types of computers). Thesystem 10 may be some other sort of electronic device, such as a copier,a scanner, a printer, a game console, a television, a set-top videodistribution or recording system, a cable box, a personal digital mediaplayer, a factory automation system, an automotive computer system, or amedical device. (The terms used to describe these various examples ofsystems, like many of the other terms used herein, may share somereferents and, as such, should not be construed narrowly in virtue ofthe other items listed.)

The data stream 12 may be one or more of a variety of types of datastreams that a user or other entity might wish to search. For example,the data stream 12 may be a stream of data received over a network, suchas packets received over the Internet or voice or data received over acellular network. The data stream 12 may be data received from a sensorin communication with the system 10, such as an imaging sensor, atemperature sensor, an accelerometer, or the like, or combinationsthereof. The data stream 12 may be received by the system 10 as a serialdata stream, in which the data is received in an order that has meaning,such as in a temporally, lexically, or semantically significant order.Or the data stream 12 may be received in parallel or out of order and,then, converted into a serial data stream, e.g., by reordering packetsreceived over the Internet. In some embodiments, the data stream 12 maypresent terms serially, but the bits expressing each of the terms may bereceived in parallel. The data stream 12 may be received from a sourceexternal to the system 10, or may be formed by interrogating a memorydevice and forming the data stream 12 from stored data.

Depending on the type of data in the data stream 12, different types ofsearch criteria may be chosen by a designer. For instance, the searchcriteria 16 may be a virus definition file. Viruses or other malware maybe characterized, and aspects of the malware may be used to form searchcriteria that indicate whether the data stream 12 is likely deliveringmalware. The resulting search criteria may be stored on a server, and anoperator of a client system may subscribe to a service that downloadsthe search criteria to the system 10. The search criteria 16 may beperiodically updated from the server as different types of malwareemerge. The search criteria may also be used to specify undesirablecontent that might be received over a network, for instance unwantedemails (commonly known as spam) or other content that a user findsobjectionable.

The data stream 12 may be searched by a third party with an interest inthe data being received by the system 10. For example, the data stream12 may be monitored for text, a sequence of audio, or a sequence ofvideo that occurs in a copyrighted work. The data stream 12 may bemonitored for utterances that are relevant to a criminal investigationor civil proceeding or are of interest to an employer.

The search criteria 16 may also include patterns in the data stream 12for which a translation is available, e.g., in memory addressable by theCPU 20 or the pattern-recognition processor 14. For instance, the searchcriteria 16 may each specify an English word for which a correspondingSpanish word is stored in memory. In another example, the searchcriteria 16 may specify encoded versions of the data stream 12, e.g.,MP3, MPEG 4, FLAC, Ogg Vorbis, etc., for which a decoded version of thedata stream 12 is available, or vice versa.

The pattern recognition processor 14 may be a hardware device that isintegrated with the CPU 20 into a single component (such as a singledevice) or may be formed as a separate component. For instance, thepattern-recognition processor 14 may be a separate integrated circuit.The pattern-recognition processor 14 may be referred to as a“co-processor” or a “pattern-recognition co-processor”.

FIG. 2 depicts an example of the pattern-recognition processor 14. Thepattern-recognition processor 14 may include a recognition module 22 andan aggregation module 24. The recognition module 22 may be configured tocompare received terms to search terms, and both the recognition module22 and the aggregation module 24 may cooperate to determine whethermatching a term with a search term satisfies a search criterion.

The recognition module 22 may include a row decoder 28 and a pluralityof feature cells 30. Each feature cell 30 may specify a search term, andgroups of feature cells 30 may form a parallel finite state machine thatforms a search criterion. Components of the feature cells 30 may form asearch-term array 32, a detection array 34, and an activation-routingmatrix 36. The search-term array 32 may include a plurality of inputconductors 37, each of which may place each of the feature cells 30 incommunication with the row decoder 28.

The row decoder 28 may select particular conductors among the pluralityof input conductors 37 based on the content of the data stream 12. Forexample, the row decoder 28 may be a one byte to 256 row decoder thatactivates one of 256 rows based on the value of a received byte, whichmay represent one term. A one-byte term of 0000 0000 may correspond tothe top row among the plurality of input conductors 37, and a one-byteterm of 1111 1111 may correspond to the bottom row among the pluralityof input conductors 37. Thus, different input conductors 37 may beselected, depending on which terms are received from the data stream 12.As different terms are received, the row decoder 28 may deactivate therow corresponding to the previous term and activate the rowcorresponding to the new term.

The detection array 34 may couple to a detection bus 38 that outputssignals indicative of complete or partial satisfaction of searchcriteria to the aggregation module 24. The activation-routing matrix 36may selectively activate and deactivate feature cells 30 based on thenumber of search terms in a search criterion that have been matched.

The aggregation module 24 may include a latch matrix 40, anaggregation-routing matrix 42, a threshold-logic matrix 44, alogical-product matrix 46, a logical-sum matrix 48, and aninitialization-routing matrix 50.

The latch matrix 40 may implement portions of certain search criteria.Some search criteria, e.g., some regular expressions, count only thefirst occurrence of a match or group of matches. The latch matrix 40 mayinclude latches that record whether a match has occurred. The latchesmay be cleared during initialization, and periodically re-initializedduring operation, as search criteria are determined to be satisfied ornot further satisfiable—i.e., an earlier search term may need to bematched again before the search criterion could be satisfied.

The aggregation-routing matrix 42 may function similar to theactivation-routing matrix 36. The aggregation-routing matrix 42 mayreceive signals indicative of matches on the detection bus 38 and mayroute the signals to different group-logic lines 53 connecting to thethreshold-logic matrix 44. The aggregation-routing matrix 42 may alsoroute outputs of the initialization-routing matrix 50 to the detectionarray 34 to reset portions of the detection array 34 when a searchcriterion is determined to be satisfied or not further satisfiable.

The threshold-logic matrix 44 may include a plurality of counters, e.g.,32-bit counters configured to count up or down. The threshold-logicmatrix 44 may be loaded with an initial count, and it may count up ordown from the count based on matches signaled by the recognition module.For instance, the threshold-logic matrix 44 may count the number ofoccurrences of a word in some length of text.

The outputs of the threshold-logic matrix 44 may be inputs to thelogical-product matrix 46. The logical-product matrix 46 may selectivelygenerate “product” results (e.g., “AND” function in Boolean logic). Thelogical-product matrix 46 may be implemented as a square matrix, inwhich the number of output products is equal the number of input linesfrom the threshold-logic matrix 44, or the logical-product matrix 46 mayhave a different number of inputs than outputs. The resulting productvalues may be output to the logical-sum matrix 48.

The logical-sum matrix 48 may selectively generate sums (e.g., “OR”functions in Boolean logic.) The logical-sum matrix 48 may also be asquare matrix, or the logical-sum matrix 48 may have a different numberof inputs than outputs. Since the inputs are logical products, theoutputs of the logical-sum matrix 48 may be logical-Sums-of-Products(e.g., Boolean logic Sum-of-Product (SOP) form). The output of thelogical-sum matrix 48 may be received by the initialization-routingmatrix 50.

The initialization-routing matrix 50 may reset portions of the detectionarray 34 and the aggregation module 24 via the aggregation-routingmatrix 42. The initialization-routing matrix 50 may also be implementedas a square matrix, or the initialization-routing matrix 50 may have adifferent number of inputs than outputs. The initialization-routingmatrix 50 may respond to signals from the logical-sum matrix 48 andre-initialize other portions of the pattern-recognition processor 14,such as when a search criterion is satisfied or determined to be notfurther satisfiable.

The aggregation module 24 may include an output buffer 51 that receivesthe outputs of the threshold-logic matrix 44, the aggregation-routingmatrix 42, and the logical-sum matrix 48. The output of the aggregationmodule 24 may be transmitted from the output buffer 51 may betransmitted to the CPU 20 (FIG. 1) on the output bus 26. In someembodiments, an output multiplexer may multiplex signals from thesecomponents 42, 44, and 48 and output signals indicative of satisfactionof criteria or matches of search terms to the CPU 20 (FIG. 1). In otherembodiments, results from the pattern-recognition processor 14 may bereported without transmitting the signals through the outputmultiplexer, which is not to suggest that any other feature describedherein could not also be omitted. For example, signals from thethreshold-logic matrix 44, the logical-product matrix 46, thelogical-sum matrix 48, or the initialization routing matrix 50 may betransmitted to the CPU in parallel on the output bus 26.

FIG. 3 illustrates a portion of a single feature cell 30 in thesearch-term array 32 (FIG. 2), a component referred to herein as asearch-term cell 54. The search-term cells 54 may include an outputconductor 56 and a plurality of memory cells 58. Each of the memorycells 58 may be coupled to both the output conductor 56 and one of theconductors among the plurality of input conductors 37. In response toits input conductor 37 being selected, each of the memory cells 58 mayoutput a value indicative of its stored value, outputting the datathrough the output conductor 56. In some embodiments, the plurality ofinput conductors 37 may be referred to as “word lines”, and the outputconductor 56 may be referred to as a “data line”.

The memory cells 58 may include any of a variety of types of memorycells. For example, the memory cells 58 may be volatile memory, such asdynamic random access memory (DRAM) cells having a transistor and acapacitor. The source and the drain of the transistor may be connectedto a plate of the capacitor and the output conductor 56, respectively,and the gate of the transistor may be connected to one of the inputconductors 37. In another example of volatile memory, each of the memorycells 58 may include a static random access memory (SRAM) cell. The SRAMcell may have an output that is selectively coupled to the outputconductor 56 by an access transistor controlled by one of the inputconductors 37. The memory cells 58 may also include nonvolatile memory,such as phase-change memory (e.g., an ovonic device), flash memory,silicon-oxide-nitride-oxide-silicon (SONOS) memory, magneto-resistivememory, or other types of nonvolatile memory. The memory cells 58 mayalso include flip-flops, e.g., memory cells made out of logic gates.

FIGS. 4 and 5 depict an example of the search-term cell 54 in operation.FIG. 4 illustrates the search-term cell 54 receiving a term that doesnot match the cell's search term, and FIG. 5 illustrates a match.

As illustrated by FIG. 4, the search-term cell 54 may be configured tosearch for one or more terms by storing data in the memory cells 58. Thememory cells 58 may each represent a term that the data stream 12 mightpresent, e.g., in FIG. 3, each memory cell 58 represents a single letteror number, starting with the letter “a” and ending with the number “9”.Memory cells 58 representing terms that satisfy the search term may beprogrammed to store a first value, and memory cells 58 that do notrepresent terms that satisfy the search term may be programmed to storea different value. In the illustrated example, the search-term cell 54is configured to search for the letter “b”. The memory cells 58 thatrepresent “b” may store a 1, or logic high, and the memory cells 58 thatdo not represent “b” may be programmed to store a 0, or logic low.

To compare a term from the data stream 12 with the search term, the rowdecoder 28 may select the input conductor 37 coupled to memory cells 58representing the received term. In FIG. 4, the data stream 12 presents alowercase “e”. This term may be presented by the data stream 12 in theform of an eight-bit ASCII code, and the row decoder 28 may interpretthis byte as a row address, outputting a signal on the conductor 60 byenergizing it.

In response, the memory cell 58 controlled by the conductor 60 mayoutput a signal indicative of the data that the memory cell 58 stores,and the signal may be conveyed by the output conductor 56. In this case,because the letter “e” is not one of the terms specified by thesearch-term cell 54, it does not match the search term, and thesearch-term cell 54 outputs a 0 value, indicating no match was found.

In FIG. 5, the data stream 12 presents a character “b”. Again, the rowdecoder 28 may interpret this term as an address, and the row decoder 28may select the conductor 62. In response, the memory cell 58representing the letter “b” outputs its stored value, which in this caseis a 1, indicating a match.

The search-term cells 54 may be configured to search for more than oneterm at a time. Multiple memory cells 58 may be programmed to store a 1,specifying a search term that matches with more than one term. Forinstance, the memory cells 58 representing the letters lowercase “a” anduppercase “A” may be programmed to store a 1, and the search-term cell54 may search for either term. In another example, the search-term cell54 may be configured to output a match if any character is received. Allof the memory cells 58 may be programmed to store a 1, such that thesearch-term cell 54 may function as a wildcard term in a searchcriterion.

FIGS. 6-8 depict the recognition module 22 searching according to amulti-term search criterion, e.g., for a word. Specifically, FIG. 6illustrates the recognition module 22 detecting the first letter of aword, FIG. 7 illustrates detection of the second letter, and FIG. 8illustrates detection of the last letter.

As illustrated by FIG. 6, the recognition module 22 may be configured tosearch for the word “big”. Three adjacent feature cells 63, 64, and 66are illustrated. The feature cell 63 is configured to detect the letter“b”. The feature cell 64 is configured to detect the letter “i”. And thefeature cell 66 is configured to both detect the letter “g” and indicatethat the search criterion is satisfied.

FIG. 6 also depicts additional details of the detection array 34. Thedetection array 34 may include a detection cell 68 in each of thefeature cells 63, 64, and 66. Each of the detection cells 68 may includea memory cell 70, such as one of the types of memory cells describedabove (e.g., a flip-flop), that indicates whether the feature cell 63,64, or 66 is active or inactive. The detection cells 68 may beconfigured to output a signal to the activation-routing matrix 36indicating whether the detection cell both is active and has received asignal from its associated search-term cell 54 indicating a match.Inactive features cells 63, 64, and 66 may disregard matches. Each ofthe detection cells 68 may include an AND gate with inputs from thememory cell 70 and the output conductor 56. The output of the AND gatemay be routed to both the detection bus 38 and the activation-routingmatrix 36, or one or the other.

The activation-routing matrix 36, in turn, may selectively activate thefeature cells 63, 64, and 66 by writing to the memory cells 70 in thedetection array 34. The activation-routing matrix 36 may activatefeature cells 63, 64, or 66 according to the search criterion and whichsearch term is being searched for next in the data stream 12.

In FIG. 6, the data stream 12 presents the letter “b”. In response, eachof the feature cells 63, 64, and 66 may output a signal on their outputconductor 56, indicating the value stored in the memory cell 58connected to the conductor 62, which represents the letter “b”. Thedetection cells 56 may then each determine whether they have received asignal indicating a match and whether they are active. Because thefeature cell 63 is configured to detect the letter “b” and is active, asindicated by its memory cell 70, the detection cell 68 in the featurecell 63 may output a signal to the activation-routing matrix 36indicating that the first search term of the search criterion has beenmatched.

As illustrated by FIG. 7, after the first search term is matched, theactivation-routing matrix 36 may activate the next feature cell 64 bywriting a 1 to its memory cell 70 in its detection cell 68. Theactivation-routing matrix 36 may also maintain the active state of thefeature cell 63, in case the next term satisfies the first search term,e.g., if the sequence of terms “bbig” is received. The first search termof search criteria may be maintained in an active state during a portionor substantially all of the time during which the data stream 12 issearched.

In FIG. 7, the data stream 12 presents the letter “i” to the recognitionmodule 22. In response, each of the feature cells 63, 64, and 66 mayoutput a signal on their output conductor 56, indicating the valuestored in the memory cell 58 connected to the conductor 72, whichrepresents the letter “i”. The detection cells 56 may then eachdetermine whether they have received a signal indicating a match andwhether they are active. Because the feature cell 64 is configured todetect the letter “i” and is active, as indicated by its memory cell 70,the detection cell 68 in the feature cell 64 may output a signal to theactivation-routing matrix 36 indicating that the next search term of itssearch criterion has been matched.

Next, the activation-routing matrix 36 may activate the feature cell 66,as illustrated by FIG. 8. Before evaluating the next term, the featurecell 64 may be deactivated. The feature cell 64 may be deactivated byits detection cell 68 resetting its memory cell 70 between detectioncycles or the activation-routing matrix 36 may deactivate the featurecell 64, for example.

In FIG. 8, the data stream 12 presents the term “g” to the row decoder28, which selects the conductor 74 representing the term “g”. Inresponse, each of the feature cells 63, 64, and 66 may output a signalon their output conductor 56, indicating the value stored in the memorycell 58 connected to the conductor 74, which represents the letter “g”.The detection cells 56 may then each determine whether they havereceived a signal indicating a match and whether they are active.Because the feature cell 66 is configured to detect the letter “g” andis active, as indicated by its memory cell 70, the detection cell 68 inthe feature cell 66 may output a signal to the activation routing matrix36 indicating that the last search term of its search criterion has beenmatched.

The end of a search criterion or a portion of a search criterion may beidentified by the activation-routing matrix 36 or the detection cell 68.These components 36 or 68 may include memory indicating whether theirfeature cell 63, 64, or 66 specifies the last search term of a searchcriterion or a component of a search criterion. For example, a searchcriterion may specify all sentences in which the word “cattle” occurstwice, and the recognition module may output a signal indicating eachoccurrence of “cattle” within a sentence to the aggregation module,which may count the occurrences to determine whether the searchcriterion is satisfied.

Feature cells 63, 64, or 66 may be activated under several conditions. Afeature cell 63, 64, or 66 may be “always active”, meaning that itremains active during all or substantially all of a search. An exampleof an always active feature cell 63, 64, or 66 is the first feature cellof the search criterion, e.g., feature cell 63.

A feature cell 63, 64, or 66 may be “active when requested”, meaningthat the feature cell 63, 64, or 66 is active when some conditionprecedent is matched, e.g., when the preceding search terms in a searchcriterion are matched. An example is the feature cell 64, which isactive when requested by the feature cell 63 in FIGS. 6-8, and thefeature cell 66, which active when requested by the feature cell 64.

A feature cell 63, 64, or 66 may be “self activated”, meaning that onceit is activated, it activates itself as long as its search term ismatched. For example, a self activated feature cell having a search termthat is matched by any numerical digit may remain active through thesequence “123456xy” until the letter “x” is reached. Each time thesearch term of the self activated feature cell is matched, it mayactivate the next feature cell in the search criterion. Thus, an alwaysactive feature cell may be formed from a self activating feature celland an active when requested feature cell: the self activating featurecell may be programmed with all of its memory cells 58 storing a 1, andit may repeatedly activate the active when requested feature cell aftereach term. In some embodiments, each feature cell 63, 64, and 66 mayinclude a memory cell in its detection cell 68 or in theactivation-routing matrix 36 that specifies whether the feature cell isalways active, thereby forming an always active feature cell from asingle feature cell.

FIG. 9 depicts an example of a recognition module 22 configured tosearch according to a first search criterion 75 and a second searchcriterion 76 in parallel. In this example, the first search criterion 75specifies the word “big”, and the second search criterion 76 specifiesthe word “cab”. A signal indicative of the current term from the datastream 12 may be communicated to feature cells in each search criterion75 and 76 at generally the same time. Each of the input conductors 37spans both of the search criteria 75 and 76. As a result, in someembodiments, both of the search criteria 75 and 76 may evaluate thecurrent term generally simultaneously. This is believed to speed theevaluation of search criteria. Other embodiments may include morefeature cells configured to evaluate more search criteria in parallel.For example, some embodiments may include more than 100, 500, 1000,5000, or 10,000 feature cells operating in parallel. These feature cellsmay evaluate hundreds or thousands of search criteria generallysimultaneously.

Search criteria with different numbers of search terms may be formed byallocating more or fewer feature cells to the search criteria. Simplesearch criteria may consume fewer resources in the form of feature cellsthan complex search criteria. This is believed to reduce the cost of thepattern-recognition processor 14 (FIG. 2) relative to processors with alarge number of generally identical cores, all configured to evaluatecomplex search criteria.

FIGS. 10-12 depict both an example of a more complex search criterionand features of the activation-routing matrix 36. The activation-routingmatrix 36 may include a plurality of activation-routing cells 78, groupsof which may be associated with each of the feature cells 63, 64, 66,80, 82, 84, and 86. For instance, each of the feature cells may include5, 10, 20, 50, or more activation-routing cells 78. Theactivation-routing cells 78 may be configured to transmit activationsignals to the next search term in a search criterion when a precedingsearch term is matched. The activation-routing cells 78 may beconfigured to route activation signals to adjacent feature cells orother activation-routing cells 78 within the same feature cell. Theactivation-routing cells 78 may include memory that indicates whichfeature cells correspond to the next search term in a search criterion.

As illustrated by FIGS. 10-12, the recognition module 22 may beconfigured to search according to complex search criteria than criteriathat specify single words. For instance, the recognition module 22 maybe configured to search for words beginning with a prefix 88 and endingwith one of two suffixes 90 or 92. The illustrated search criterionspecifies words beginning with the letters “c” and “l” in sequence andending with either the sequence of letters “ap” or the sequence ofletters “oud”. This is an example of a search criterion specifyingmultiple target expressions, e.g., the word “clap” or the word “cloud”.

In FIG. 10, the data stream 12 presents the letter “c” to therecognition module 22, and feature cell 63 is both active and detects amatch. In response, the activation-routing matrix 36 may activate thenext feature cell 64. The activation-routing matrix 36 may also maintainthe active state of the feature cell 63, as the feature cell 63 is thefirst search term in the search criterion.

In FIG. 11, the data stream 12 presents a letter “l”, and the featurecell 64 recognizes a match and is active. In response, theactivation-routing matrix 36 may transmit an activation signal both tothe first feature cell 66 of the first suffix 90 and to the firstfeature cell 82 of the second suffix 92. In other examples, moresuffixes may be activated, or multiple prefixes may active one or moresuffixes.

Next, as illustrated by FIG. 12, the data stream 12 presents the letter“o” to the recognition module 22, and the feature cell 82 of the secondsuffix 92 detects a match and is active. In response, theactivation-routing matrix 36 may activate the next feature cell 84 ofthe second suffix 92. The search for the first suffix 90 may die out, asthe feature cell 66 is allowed to go inactive. The steps illustrated byFIGS. 10-12 may continue through the letters “u” and “d”, or the searchmay die out until the next time the prefix 88 is matched.

In some embodiments, the pattern recognition functionality provided bythe pattern-recognition processor 14 may be added to an existing systemor device having a microcontroller. For example, the pattern-recognitionprocessor 14 may be connected to the microcontroller as a peripheraldevice (e.g., a device external to the microcontroller), or some or allof the pattern-recognition functionality may be added to themicrocontroller via additional software, firmware, and/or hardware. Ineither case, the microcontroller may use additional memory forproviding, storing, and processing the data stream 12. For example, amicrocontroller may provide search terms to an external device orreceive search results from the external device. In such an embodiment,the external device may include volatile or non-volatile memory, e.g.,DRAM, SRAM, Flash, ROM, PROM, EEPROM, etc. The peripheral device mayalso include functionality such as pattern recognition, dataacquisition, or any other suitable functionality.

FIG. 13 illustrates an embodiment of a single-chip microcontroller 94and a peripheral device 96 accessible by the microcontroller 94 over amicrocontroller bus 98. The microcontroller 94 may include anyfunctionality, such as data processing, data storage, interfaces, etc.Because of the integrated functionalities provided in themicrocontroller 94, in a typical embodiment, the microcontroller 94 doesnot provide any memory management, bus translation, or other externallyaccessible functions or components to enable the addition of theperipheral device 96. As mentioned above, in some embodiments theperipheral device may include some type of memory, such as DRAM.

The peripheral device 96 may include a self-selecting bus decoder 100.As described further below, the self-selecting bus decoder 100 receivesa memory mapping configuration and self-selects memory access, asrequested by a signal from the microcontroller 94 on each bus-cycle. Thebus decoder 100 may receive signals from the microcontroller 94 over themicrocontroller bus 98 and may also receive decode set-up and controlsignal 102. The self-selecting bus decoder 100 enables the addition ofthe peripheral device 96 to the microcontroller 94 without adding anycomponents to the microcontroller 94 or between the peripheral device 96and the microcontroller 94. Thus, the peripheral device 96 may be addedto a printed circuit assembly (PCA) containing the microcontroller 94and connected via printed circuit traces to the microcontroller 94.

FIG. 14 illustrates the self-selecting bus decoder 100, and includedlogic, in further detail. The self-selecting bus decoder 100 may includeaddress-matching and mapping logic 104 and bus-cycle validation logic106. The function provided by the peripheral device 96, such as datastorage and/or data processing via included memory, is illustrated bythe peripheral function block 108. As described above, the peripheraldevice 96 and the microcontroller 94 may communicate over amicrocontroller bus 98. Any signals provided from the microcontroller 94pass over the microcontroller bus 98 to the self-selecting decoder 100.The self-selecting decoder 100 processes any signals received from themicrocontroller 94 and, as described further below, determines if theperipheral device should provide a response to the signal. The outputfrom the peripheral device 96 may be provided to the microcontroller 94over the microcontroller bus 98.

The address-matching and mapping logic 104 of the decoder 100 receivesthe decode set-up and control signal 102. The decode set-up and controlsignal 102 provides a memory mapping configuration to theaddress-matching and mapping logic 104. The decode set-up and controlsignal 102 may convey any other signals that configure the decoder 100.In some embodiments, the decode set-up and control signal 102 may beconfigured by electrically connecting pins or other electricalconnections on the PCA, e.g., after connection of the peripheral device96 to the PCA. The memory mapping configuration provided by the decodeset-up and control signal 102 may specify a range of memory addressesprovided by memory of the peripheral device 96, and/or a range of memoryaddresses provided by the microcontroller 94. For a given memory addressrange, the address-matching and mapping logic 104 may determine if theperipheral device 96 should respond to this address range, i.e., if thememory address range is “mapped” to the peripheral device 96.

In a bus cycle, the address-matching and mapping logic 104 may receive asignal from the microcontroller 94 that includes a memory address. Basedon the memory mapping configuration provided by the decode set-up andcontrol signal 102 and the memory address, the address-matching andmapping logic 104 may determine if the peripheral device 96 should beselected. If the memory address is in the range of memory addressesprovided by the peripheral device 96, then the peripheral device 96 maybe selected to fulfill any memory operation requested in the signalprovided by the microcontroller 94.

The bus-cycle-validation logic 106 identifies the memory operationprovided to the peripheral device 96 from the microcontroller 94. Arequest for a memory operation may be provided in the signal sent to theperipheral device 94 over the microcontroller bus 98. As stated above,this signal may also include a memory address, in addition to a requestfor a memory operation. For example, the bus-cycle validation logic 106may determine if the requested operation is a direct memory access (DMA)operation, write, read, refresh, and/or any other operation. Thebus-cycle validation logic 106 determines if a response may be providedby the peripheral device 96 and what type of response to provide.

If the bus-cycle validation logic 106 determines that the request fromthe microcontroller 94 may be properly satisfied by the peripheraldevice 96, the bus-cycle validation logic 106 may provide a cycle-enablesignal 112 to initiate the peripheral function 108. The cycle-enablesignal selects the peripheral function 108 of the peripheral device 96to respond to the memory request. The peripheral function 108 providesthe appropriate response to the memory request received from themicrocontroller 94, such as write, read, refresh, etc. For example, in aread request, the peripheral function 108 may provide data to themicrocontroller 94 over the microcontroller bus 98, such as the contentsof the data at the specified memory address. Further, the responseprovided by the peripheral function block 108 may also provide statusinformation to the microcontroller 94, such as an indication of thecompletion of the current operation, errors, etc.

It should be appreciated that the address-matching and mapping logic 104and the bus-cycle validation logic 106 operate in parallel in eachbus-cycle. That is, for each bus-cycle, the operations performed by eachlogic block of the self-select bus decoder 100 are executed in a singlebus-cycle. For each memory operation requested by the microcontroller94, the self-selecting bus decoder 100 determines if the request may beresponded to by the peripheral device 96, determines if the requestrequires a response from the peripheral device 96, and selects theperipheral device 96 to provide the appropriate response.

In some embodiments, a peripheral device with a self-selecting busdecoder 100 may include a bus translator, as further described in U.S.patent application Ser. No. 12/265,436 filed on Nov. 5, 2008, titled“Bus Translator,” by Harold B Noyes et al. FIG. 15 depicts an embodimentillustrating the microcontroller 94 coupled to a peripheral device 116having a self-selecting bus decoder 118 and a bus translator 120. Thebus translator 120 and the self-selecting bus decoder 118 maycommunicate over an internal bus 122. The internal bus 122 provides anytranslated signals from the bus translator 120 to the self-selecting busdecoder 118. As described above, the self-selecting bus decoder 118includes address-matching and mapping logic 124 and bus-cycle validationlogic 126, and may provide a cycle-enable signal 128 to enable aperipheral function 130. As also described above, the address-matchingand mapping logic 124 may receive a memory mapping configuration via adecode set-up and control signal 132.

The bus translator 120 may be configured to translate signals on each ofthe plurality of different types of buses 134 into signals that areappropriate for the self-selecting bus decoder 118 of the peripheraldevice 116 to receive through the internal bus 122 and vice-versa. Tofacilitate operation over the plurality of different types of buses 134,the bus translator may include a plurality of bus drivers 136 (e.g.,drivers A-E), and a plurality of bus physical interfaces 138 (e.g., busA-E I/O pins) The bus translator 120 may include a multiplexer or ademultiplexer to increase or decrease the number of signals that conveydata between the internal bus 122 and a selected one of the plurality ofdifferent buses 134. The bus translator 120 may also be configured toadjust the timing of signals that convey data between the internal bus122 and the selected one of the plurality of different buses 134 to beappropriate for each of the buses 134 and 122. The bus translator 120may also be configured to adjust the voltage of signals conveying databetween the internal bus 122 and the selected one of the plurality ofdifferent buses 134.

A control signal 140 may convey signals that configure the bustranslator 120. For example, the control signal 140 may convey a signalthat configures the bus translator 120 to select one of the differenttypes of buses 134. In some embodiments, the control signal 140 mayconvey data that is stored in registers in the bus translator 120. Inother embodiments, the control signal 140 may be omitted (which is notto suggest that any other feature described herein may not also beomitted), and the bus translator 120 may be configured by blowing fuseswithin the bus translator 120 during manufacturing or by electricallyconnecting pins or other electrical connections on the peripheral device116, e.g., with a jumper, after the peripheral device 116 ismanufactured. The peripheral device 116 may be configured toautomatically detect which of the different types of buses 134 is beingused, e.g., by selecting a bus based on which of the physical businterfaces 138 is connected to an external bus.

The plurality of different buses 134 may include several different typesof buses. For example, the plurality of different buses 134 may includean asynchronous bus with non-multiplexed address and data, anasynchronous bus with multiplexed address and data, a synchronous buswith non-multiplexed address and data, a synchronous bus withmultiplexed address and data, a synchronous dynamic random access memory(SDRAM) bus, a double data rate (DDR) bus, a DDR2 bus, a DDR3 bus, aDDR4 bus, a PCI bus, a PCI express bus, a PCIx bus, a security gatewaymanagement interface (SGMI) bus, or other types of buses.

The peripheral device 116 may communicate with the microcontroller 94through a microcontroller bus 144. The microcontroller bus 144 may beone of the types of buses that are compliant with the plurality ofdifferent buses 134 coupled to the bus translator 120 within theperipheral device 116. The microcontroller bus 144 may couple to thephysical bus interface 138 that is appropriate for the microcontrollerbus 144. For example, if the microcontroller bus 144 is a DDR2 bus, itmay couple to a physical bus interface 138 that is compliant with theDDR2 bus specification. The other physical bus interfaces may remainunused.

As data is conveyed between the microcontroller 94 and the peripheraldevice 116, the bus translator 120 may translate the signals.Translating the signals may include multiplexing or demultiplexing thesignals, increasing or decreasing the timing of the signals, or changingthe voltage of the signals. Regardless of which of the plurality ofdifferent buses 134 is selected, the translated signals on the internalbus 122 may be similar or the same, and the bus translator 120 may beconfigured to receive the signals and transmit the signals through theinternal bus 122.

As described above, the microcontroller 94 may request one or morememory operations in a signal sent to the peripheral device 116. In theembodiment depicted in FIG. 15, the signal is first received by the bustranslator 120 through the physical bus interface 138 and one of theplurality of different buses 134. After the signal is translated throughthe bus translator 120, the self-selecting bus decoder 118 may processthe signal as described above. For example, the address-matching andmapping logic 124 may determine if a memory address of the signal isprovided by the memory of the peripheral device 116, and the bus-cyclevalidation logic 126 may determine the type of memory operation and theappropriate response. If the self-selecting bus decoder 118 determinesthat the peripheral device 116 can respond to the request from themicrocontroller 94, the self-selecting bus decoder 118 may output thecycle enable signal 128 to select the peripheral function 130 of theperipheral device 116. Any response provided by the peripheral function130 may be sent as an output signal to bus translator 120 via theinternal bus 122. The bus translator 120 can translate the output signalof the peripheral function 130 to the selected one of the plurality ofdifferent buses 134. The response, e.g., the output signal from theperipheral function 130, is then sent over the microcontroller bus 144to the microcontroller 94.

FIG. 16 illustrates an example of a process 150 for operating aperipheral device with a self-selecting bus decoder. The process 150 maybegin with selecting a bus from among a plurality of different busesavailable to peripheral device (block 152). Selecting one bus among theplurality of different buses may be performed after or during themanufacture of the device. The plurality of different types of buses mayinclude any of those described above. The device may be configured tocommunicate through two or more buses, three or more buses, four or morebuses, five or more buses, or six or more buses. Alternatively, asdiscussed above, certain embodiments may omit a bus translator andconfiguration of bus type, e.g., if the microcontroller and peripheraldevice communicate over the same or a similar bus.

The peripheral device may be coupled to a microcontroller through theselected bus (block 154). Coupling the peripheral device to themicrocontroller through the selected bus may include installing thedevice on a PCA, e.g. a system board, motherboard, etc.

A memory mapping configuration may be specified (block 156), such asthrough pins or other electrical connections on the PCA, that maps arange of address to the peripheral device and/or a range of addresses tothe microcontroller. As described above, the self-selecting bus decoderof the peripheral device may receive a decode set-up and control signalthat provides the memory mapping configuration (block 158).

The microcontroller coupled to the peripheral device may make a requestfor a memory operation at a certain memory address or addresses, such asby sending a signal over the selected bus, i.e., one of the busesselected from one of the plurality of different buses coupled to the bustranslator, to the peripheral device (block 160). The bus translator maytranslate the request from the microcontroller and provide thetranslated request to the self-selecting bus decoder over an internalbus of the device (block 162).

As described above, in a bus-cycle, the self-selecting bus decoder mayexecute the address-matching and mapping logic (block 164) and thebus-cycle validation logic (block 166) in parallel. The address-matchingand mapping logic determines that the memory address or addresses of therequest are in the range of memory addresses provided by the peripheraldevice (block 164). The bus-cycle validation logic determines the typeof memory operation of the request and determines the appropriateresponse (block 166).

After processing by the address-matching and mapping logic and thebus-cycle validation logic, the self-selecting bus decoder may enablethe peripheral device to respond to the request (block 168), e.g.,through a cycle-enable signal provided to a function of the peripheraldevice. The response to the request is provided to the bus translator(block 170). The bus translator translates the response and sends theresponse to the microcontroller (block 172), such as by sending a signalover the selected one of the plurality of different buses coupled to thebus translator.

The process 150 is believed to reduce the cost and difficulty of addingfunctionality to microcontrollers via addition of a peripheral device.Because the peripheral device may self-select based on a requestedmemory operation from the microcontroller and may communicate through avariety of different types of buses, the peripheral device may be usedand coupled to a microcontroller without the addition of othercomponents to the microcontroller or between the peripheral device andthe microcontroller.

While the invention may be susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, it should be understood that the invention is not intended tobe limited to the particular forms disclosed. Rather, the invention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the followingappended claims.

What is claimed is:
 1. A system, comprising: a microcontroller; and adevice coupled to the microcontroller via a bus, wherein the devicecomprises a self-selecting bus decoder configured to: receive a memorymapping configuration; receive a request from the microprocessor; anddetermine if the device should provide a response to the request fromthe microcontroller, based at least in part upon the memory mappingconfiguration.
 2. The system of claim 1, wherein the device comprises apattern recognition processor.
 3. The system of claim 1, wherein thedecoder is configured to receive the memory mapping configuration via adecode set-up and control signal independent from the request.
 4. Thesystem of claim 1, wherein the memory mapping configuration comprises anindication of a plurality of memory addresses provided by the device. 5.The system of claim 1, wherein the memory mapping configurationcomprises an indication of a plurality of memory addresses provided bythe microcontroller.
 6. The system of claim 1, wherein the decoder isconfigured to determine that the device should provide the response whena memory address associated with the request is provided by the devicebased on the memory mapping configuration.
 7. The system of claim 1,wherein the device comprises double data rate two (DDR2) RAM.
 8. Thesystem of claim 1, wherein the request comprises a memory read, a memorywrite, a memory refresh, a DMA request, or any combination thereof. 9.The system of claim 3, wherein the decoder is configured to determine atype of the request.
 10. The system of claim 3, wherein the decoder isconfigured to determine a response to the request.
 11. A method,comprising: receiving a request from a microcontroller via a bus;determining a memory address of the request; determining if the memoryaddress is provided by an external device coupled to the microcontrollervia the bus; determining a type of the memory request; and determining aresponse to the memory request.
 12. The method of claim 11, comprisingproviding a response from the external device to the microcontroller.13. The method of claim 11, comprising receiving a memory mappingconfiguration at the external device.
 14. The method of claim 12,comprising providing data from the external device.
 15. The method ofclaim 12, wherein determining a response to the memory request comprisesselecting a function of the external device.
 16. A device, comprising: aself-selecting bus decoder comprising logic configured to: receive amemory mapping configuration; receive a request via a microcontrollerbus; and determine if the device should provide a response to therequest, based at least in part upon the memory mapping configuration.17. The device of claim 16, comprising logic to determine a type of therequest and a response to the request.
 18. The device of claim 16,comprising logic configured to provide a signal to enable the device torespond to the request.
 19. The device of claim 16, wherein the decoderis configured to receive a memory mapping configuration.
 20. The deviceof claim 16, wherein the decoder is configured to determine that thedevice should provide the response when a memory address associated withthe request is associated with at least one of a plurality of memoryaddresses indicated by the memory mapping configuration.
 21. A device,comprising: a pattern-recognition processor; and a decoder comprisinglogic configured to: select the device in response to a request from amicrocontroller coupled to the device; and determine if a memory addressreceived from the microcontroller is provided by the device.